A video of America's only current prisoner of war has been handed to the US government, showing he is still alive more than four years after he went missing, according to the military newspaper Stars and Stripes.

The video footage, which reportedly shows a frail Sergeant Bowe Bergdahl referencing the 5 December death of Nelson Mandela, is the first to surface in nearly three years.

It has not been made public, but an unnamed defence official confirmed its authenticity to Stars and Stripes, a paper partly funded by the US military.

The official declined to say when exactly the video was made, or how it was obtained.

Bergdahl, 27, disappeared from a base in eastern Afghanistan in June 2009. He is thought to have been taken by the Taliban across the porous mountain border into Pakistan, where both tracing him and any potential rescue would be far more complicated.

His captors are generally believed to be the Haqqani network, perhaps the most ruthless and feared branch of the insurgency.

The US government has been trying for several years to negotiate his release through a prisoner exchange, which would free several high-profile detainees from the Guantánamo Bay prison, but has had little success in the stop-start efforts.

Bergdahl's parents, who last year received a letter that appeared to be from their son, welcomed the first images of him since early 2011, and repeated their plea for his freedom.

"Naturally, this is very important to us and our resolve to continue our efforts to bring Bowe home as soon as possible," said the statement, released through the Idaho National Guard.

"As we have done so many times over the past four and a half years, we request his captors to release him safely so that our only son can be reunited with his mother and father," NBC news quoted the statement as saying.

"BOWE – If you see this, continue to remain strong through patience. Your endurance will carry you to the finish line. Breathe!" the statement said.